As stated in the title: is there any evidence that the hormones etc that the body produces during intercourse increases one's likelihood of encountering a bear in the back-country?
There is at least one documented incident with a bear that occurred in the 1980s which may have been related sexual intercourses.
Unfortunately the two teenagers, Jane Ammerman and Kim Eberly, did not survive.
Stephen Herrero wrote about the incident in his book titled Bear Attacks: Their Causes and Avoidance:
In my opinion, there are other risk factors of bigger importance that I would try to address first.